Just buy one with as few additives as possible - and store in an airtight container or vacuum-saver bag. As I recall - Roland makes a nice Panko that's made in the USA. I think Trader Joe's label also makes a respectable Panko. There are myriads more Japanese labels if you go to a Japanese grocer, but be careful to look at the ingredients because some are panko mixes for special recipe purposes and not the plain type.

we bake a lot of bread here...so we occasionally cube a stale ciabatta or sourdough loaf from 3 days ago... bake at 300+/- until dry and crunchy. bag some for the next caesar salad and toss in the cuisanart processing until as fine or coarse as desired. store in freezer. always have some on hand. running out of bread crumbs is almost a crisis. sometimes we toss the cubes in some olive oil and herbs before roasting.